Pratt Kara G, Dong Wei, Aizenman Carlos D
Department of Neuroscience, Brown University, Box G-LN, Providence, Rhode Island 02912, USA.
Nat Neurosci. 2008 Apr;11(4):467-75. doi: 10.1038/nn2076. Epub 2008 Mar 23.
Much of the information processing in the brain occurs at the level of local circuits; however, the mechanisms underlying their initial development are poorly understood. We sought to examine the early development and plasticity of local excitatory circuits in the optic tectum of Xenopus laevis tadpoles. We found that retinal input recruits persistent, recurrent intratectal synaptic excitation that becomes more temporally compact and less variable over development, thus increasing the temporal coherence and precision of tectal cell spiking. We also saw that patterned retinal input can sculpt recurrent activity according to a spike timing-dependent plasticity rule, and that impairing this plasticity during development results in abnormal refinement of the temporal characteristics of recurrent circuits. This plasticity is a previously unknown mechanism by which patterned retinal activity allows intratectal circuitry to self-organize, optimizing the temporal response properties of the tectal network, and provides a substrate for rapid modulation of tectal neuron receptive-field properties.
大脑中的许多信息处理都发生在局部回路水平；然而，其初始发育背后的机制却知之甚少。我们试图研究非洲爪蟾蝌蚪视顶盖中局部兴奋性回路的早期发育和可塑性。我们发现，视网膜输入会引发持续的、反复的顶盖内突触兴奋，这种兴奋在发育过程中在时间上变得更加紧凑且变异性更小，从而增加了顶盖细胞放电的时间相干性和精确性。我们还发现，有模式的视网膜输入可以根据依赖于放电时间的可塑性规则塑造反复活动，并且在发育过程中损害这种可塑性会导致反复回路时间特征的异常精细化。这种可塑性是一种此前未知的机制，通过它有模式的视网膜活动使顶盖内电路能够自我组织，优化顶盖网络的时间响应特性，并为快速调节顶盖神经元感受野特性提供了基础。
